The role of blood glucose in defense of plasma volume during hemorrhage

Association between Blood Glucose and cardiac Rhythms during pre-hospital care of Trauma Patients - a retrospective Analysis

Background

Deranged glucose metabolism is frequently observed in trauma patients after moderate to severe traumatic injury, but little data is available about pre-hospital blood glucose and its association with various cardiac rhythms and cardiac arrest following trauma.

Methods

We retrospectively investigated adult trauma patients treated by a nationwide helicopter emergency medical service (34 bases) between 2005 and 2013. All patients with recorded initial cardiac rhythms and blood glucose levels were enrolled. Blood glucose concentrations were categorised; descriptive and regression analyses were performed.

Results

In total, 18,879 patients were included, of whom 185 (1.0%) patients died on scene. Patients with tachycardia (≥100/min, 7.0 ± 2.4 mmol/L p < 0.0001), pulseless ventricular tachycardia (9.8 ± 1.8, mmol/L, p = 0.008) and those with ventricular fibrillation (9.0 ± 3.2 mmol/L, p < 0.0001) had significantly higher blood glucose concentrations than did patients with normal sinus rhythm between 61 and 99/min (6.7 ± 2.1 mmol/L). In patients with low (≤2.8 mmol/L, 7/79; 8.9%, p < 0.0001) and high (> 10.0 mmol/L, 70/1271; 5.5%, p < 0.0001) blood glucose concentrations cardiac arrest was more common than in normoglycaemic patients (166/9433, 1.8%). ROSC was more frequently achieved in hyperglycaemic (> 10 mmol/L; 47/69; 68.1%) than in hypoglycaemic (≤4.2 mmol/L; 13/31; 41.9%) trauma patients (p = 0.01).

Conclusions

In adult trauma patients, pre-hospital higher blood glucose levels were related to tachycardic and shockable rhythms. Cardiac arrest was more frequently observed in hypoglycaemic and hyperglycaemic pre-hospital trauma patients. The rate of ROSC rose significantly with rising blood glucose concentration. Blood glucose measurements in addition to common vital parameters (GCS, heart rate, blood pressure, breathing frequency) may help identify patients at risk for cardiopulmonary arrest and dysrhythmias.

Preinjury Fed State Alters the Physiologic Response in a Porcine Model of Hemorrhagic Shock and Polytrauma

INTRODUCTION

Hemorrhagic shock and injury lead to dramatic changes in metabolic demands and continue to be a leading cause of death. We hypothesized that altering the preinjury metabolic state with a carbohydrate load prior to injury would affect subsequent metabolic responses to injury and lead to improved survival.

METHODS

Sixty-four pigs were randomized to fasted (F) or carbohydrate prefeeding (CPF) groups and fasted 12 h prior to experiment. The CPF pigs received an oral carbohydrate load 1 h prior to anesthesia. All pigs underwent a standardized injury/hemorrhagic shock protocol. Physiologic parameters and laboratory values were obtained at set time points.

RESULTS

Carbohydrate prefeeding did not convey a survival benefit; instead, CPF animals had greater mortality rates (47% vs. 28%; P = 0.153; log-rank [Mantel-Cox]). Carbohydrate prefeeding animals also had higher rates of acute lung injury (odds ratio, 4.23; 95% confidence interval, 1.1-16.3) and altered oxygen utilization. Prior to shock and throughout resuscitation, CPF animals had significantly higher serum glucose levels than did the F animals.

CONCLUSIONS

Carbohydrate prefeeding did not provide a survival benefit to swine subjected to hemorrhagic shock and polytrauma. Carbohydrate prefeeding led to significantly different metabolic profile than in fasted animals, and prefeeding led to a greater incidence of lung injury, increased multiorgan dysfunction, and altered oxygen utilization.

A four-compartment metabolomics analysis of the liver, muscle, serum, and urine response to polytrauma with hemorrhagic shock following carbohydrate prefeed

Objective

Hemorrhagic shock accompanied by injury represents a major physiologic stress. Fasted animals are often used to study hemorrhagic shock (with injury). A fasted state is not guaranteed in the general human population. The objective of this study was to determine if fed animals would exhibit a different metabolic profile in response to hemorrhagic shock with trauma when compared to fasted animals.

Methods

Proton (1H) NMR spectroscopy was used to determine concentrations of metabolites from four different compartments (liver, muscle, serum, urine) taken at defined time points throughout shock/injury and resuscitation. PLS-DA was performed and VIP lists established for baseline, shock and resuscitation (10 metabolites for each compartment at each time interval) on metabolomics data from surviving animals.

Results

Fed status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The death rate for CPF animals is higher than FS animals (47 vs 28%). The majority of deaths occur post-resuscitation suggesting reperfusion injury. The metabolomics response to shock reflects priorities evident at baseline. FS animals raise the baseline degree of proteolysis to provide additional amino acids for energy production while CPF animals rely on both glucose and, to a lesser extent, amino acids. During early resuscitation levels of metabolites associated with energy production drop, suggesting diminished demand.

Conclusions

Feeding status prior to the occurrence of hemorrhagic shock with injury alters the metabolic course of this trauma and potentially affects mortality. The response to shock reflects metabolic priorities at baseline.

Hemodynamic responses elicited by systemic injections of isotonic and hypertonic saline in hemorrhaged rats

PURPOSE

The objectives of this study were (i) to characterize the hemodynamic responses caused by controlled hemorrhage (HEM) in pentobarbital-anesthetized rats, and (ii) to determine the responses elicited by systemic bolus injections of isotonic saline (0.15M) or hypertonic saline (3M) given 5min after completion of HEM.

RESULTS

Controlled HEM (4.3±0.2ml/rat at 1.5ml/min) resulted in a pronounced and sustained fall in mean arterial blood pressure (MAP) to about 40mmHg. The fall in MAP was associated with a reduction in hindquarter vascular resistance (HQR) but no changes in renal (RR) or mesenteric (MR) vascular resistances. Systemic injections of isotonic saline (96-212μmol/kg i.v., in 250-550μl) did not produce immediate responses but promoted the recovery of MAP to levels below pre-HEM values. Systemic injections of hypertonic saline (750-3000μmol/kg, i.v., in 250-550μl) produced immediate and pronounced falls in MAP, RR, MR and especially HQR of 30-120s in duration. However, hypertonic saline prompted a full recovery of MAP, HQR and RR to pre-HEM levels and an increase in MR to levels above pre-HEM values.

CONCLUSIONS

This study demonstrates that (i) HEM induced a pronounced fall in MAP which likely involved a fall in cardiac output and HQR, (ii) isotonic saline did not fully normalize MAP, and (iii) hypertonic saline produced dramatic initial responses, and promoted normalization of MAP probably by restoring blood volume and cardiac output through sequestration of fluid from intracellular compartments.

Arterial blood gases, electrolytes, and metabolic indices associated with hemorrhagic shock: inter- and intrainbred rat strain variation

We have previously shown interstrain variation (indicating a genetic basis), and intrastrain variation in survival time after hemorrhage (STaH) among inbred rat strains. To assist in understanding physiological mechanisms associated with STaH, we analyzed various arterial blood measures (ABM; pH, Paco2, oxygen content, sodium, potassium, glucose, bicarbonate, base excess, total CO2, and ionized calcium) in inbred rats. Rats from five inbred strains (n = 8-10/strain) were catheterized and, ≈ 24 h later, subjected to a conscious, controlled, 47% hemorrhage. ABM were measured at the start (initial) and end (final) of hemorrhage. Inter- and intrainbred strain variations of ABM were quantified and compared, and correlations of ABM with STaH were determined. All final ABM values and some initial ABM values were different among strains. Most ABM changed (Δ) during hemorrhage, and these changes differed among strains (P <0.03). Some strain-dependent correlations (r ≥ 0.7; P ≤ 0.05) existed between ΔABM and STaH (e.g., BN/Mcwi, ΔK(+), r = -0.84). Dark Agouti rats (longest STaH) had the smallest ΔPaco2, ΔHCO3(-), and Δbase excess, and the highest final glucose. High coefficients of variation (CVs, >10%), strain-specific CVs, and low intraclass correlation coefficients (rI < 0.5) defined the large intrastrain ABM variation that exceeded interstrain variation for most ABM. These results suggest that some ABM (K(+), Paco2, glucose, oxygen content) could predict subsequent STaH in an inbred rat strain-dependent manner. We speculate that whereas genetic differences may be responsible for interstrain variation, individual-specific epigenetic processes (e.g., DNA methylation) may be partly responsible for both inter- and intrastrain ABM variation.

Hyperpressure intraperitoneal fluid administration for control of bleeding after liver injury

BACKGROUND

Acute hemorrhage is the principal cause of death in trauma patients, with most fatalities occurring during the pre-hospital phase. Recently, intra-abdominal insufflation by carbon dioxide has been shown to drastically reduce bleeding in vascular and splanchnic hemorrhagic animal models simulating the pre-hospital phase. Here, we propose that using dialysate fluid for increasing intra-abdominal pressure is at least as effective as gas with some potential advantages.

MATERIALS AND METHODS

A novel method of inducing liver trauma was used in 24 White New Zealand rabbits randomized into three groups: intra-abdominal carbon dioxide insufflation (GAS) with 15 cm H(2)O pressure; intra-abdominal infusion of type III dialysate solution (DIAL) with the same pressure; no change in intra-abdominal pressure (CTRL). All groups received intravenous resuscitation when their mean arterial pressure was below 30 mmHg. Physiologic parameters were recorded during 20 min of bleeding.

RESULTS

Red blood cell (RBC) volume loss in the DIAL and GAS was 45% and 48% lower than that in the CTRL, respectively (P < 0.0005). Similar trends were observed for losses in RBC count and hemoglobin (Hb). Final mean arterial pressure, arterial RBC, Hb, and hematocrit were higher in the DIAL and GAS than in the CTRL; glucose concentration in the DIAL group was significantly higher than that in the GAS and CTRL groups. No intravenous fluid therapy was needed in the DIAL group.

CONCLUSIONS

Hyperpressure intraperitoneal dialysate administration successfully reduced bleeding after severe liver injury in rabbits. This method can potentially be used as an adjunct to increase patient survival during pre-hospital cares.

The role of protein O-linked beta-N-acetylglucosamine in mediating cardiac stress responses

The modification of serine and threonine residues of nuclear and cytoplasmic proteins by O-linked beta-N-acetylglucosamine (O-GlcNAc) has emerged as a highly dynamic post-translational modification that plays a critical role in regulating numerous biological processes. Much of our understanding of the mechanisms underlying the role of O-GlcNAc on cellular function has been in the context of its adverse effects in mediating a range of chronic disease processes, including diabetes, cancer and neurodegenerative diseases. However, at the cellular level it has been shown that O-GlcNAc levels are increased in response to stress; augmentation of this response improved cell survival while attenuation decreased cell viability. Thus, it has become apparent that strategies that augment O-GlcNAc levels are pro-survival, whereas those that reduce O-GlcNAc levels decrease cell survival. There is a long history demonstrating the effectiveness of acute glucose-insulin-potassium (GIK) treatment and to a lesser extent glutamine in protecting against a range of stresses, including myocardial ischemia. A common feature of these approaches for metabolic cardioprotection is that they both have the potential to stimulate O-GlcNAc synthesis. Consequently, here we examine the links between metabolic cardioprotection with the ischemic cardioprotection associated with acute increases in O-GlcNAc levels. Some of the protective mechanisms associated with activation of O-GlcNAcylation appear to be transcriptionally mediated; however, there is also strong evidence to suggest that transcriptionally independent mechanisms also play a critical role. In this context we discuss the potential link between O-GlcNAcylation and cardiomyocyte calcium homeostasis including the role of non-voltage gated, capacitative calcium entry as a potential mechanism contributing to this protection.

Rat strains bred for low and high aerobic running capacity do not differ in their survival time to hemorrhage

Hemorrhagic shock reflects low tissue perfusion that is inadequate to maintain normal metabolic functions. Often associated with this condition are impairments in cellular oxygen delivery and utilization. Rat strains divergent in their running endurance have been artificially selected over 12 generations. As these rats bred for high (HCR) vs low (LCR) aerobic running capacity have greater tissue O(2) utilization capacity and improved cardiovascular function, we hypothesized that HCR would be more tolerant (i.e., have greater survivability) to the global ischemia of hemorrhagic shock than LCR. To address this hypothesis, survival time to a severe-as substantiated by dramatic changes in plasma lactate, HCO(3), and base deficit-controlled hemorrhage was measured. Male rats were catheterized and, approximately 24 h later, an estimated >35% of the calculated blood volume was removed during a 26-min period while the rats were conscious and unrestrained. Rats were observed for 6 h or until death. Contrary to our hypothesis, survival time in HCR (220 +/- 63 min; n = 6) did not differ statistically (P = 0.46) from that in LCR (279 +/- 53 min; n = 7). Similarly, there were no statistical differences (P >or= 0.08) between rat lines in blood pH, lactate, HCO(3), and base deficit pre- or post-hemorrhage. In addition, few significant differences between lines in response to hemorrhage were detected by measures of cellular antioxidant status in heart, liver, or lung. Since animals with genetically greater tissue oxygen utilization capacity failed to show longer survival times, our results suggest that other mechanisms must play a more dominant role in determining survivability to hemorrhage under conditions of this hemorrhage.

Uncontrolled hemorrhage in insulin-dependent diabetic rats

OBJECTIVES

Diabetes mellitus (DM) is a known risk factor for higher morbidity and mortality after trauma. The authors tested the hypothesis that there is a difference in the response to uncontrolled hemorrhage between normal euglycemic rats and insulin-dependent diabetic rats.

METHODS

Thirty-one adult male Sprague-Dawley rats were used in this study. Fifteen streptozocin (STZ)-injected rats became diabetic (DM+) 2 weeks after treatment. Sixteen rats served as nondiabetic controls (DM-). All rats were anesthetized with Althesin and their femoral arteries were catheterized via cutdown, allowing continuous monitoring of vital signs. Sixteen (eight DM-, eight DM+) rats underwent uncontrolled hemorrhage by 75% tail amputation. Fifteen (eight DM-, seven DM+) rats served as non-hemorrhage controls. The mean arterial pressure (MAP), lactate, and cumulative hemorrhage volume per 100 g were measured pre-hemorrhage and then every 15 minutes post-hemorrhage for 2 hours. Data were reported as mean +/- standard deviation. Interval data were analyzed by analysis of variance (two tails, alpha = 0.05).

RESULTS

Pre-hemorrhage glucose was significantly higher (p < 0.001) in the DM+ (357.9 +/- 22.2 mg/dL) versus DM- (125.7 +/- 9.7 mg/dL) rats. At baseline, there was no significant difference in weight, MAP, or lactate between DM+ and DM- rats. Body-weight-adjusted mean cumulative hemorrhage volume was significantly greater (p < 0.04) in diabetic rats (2.52 +/- 0.15 cm(3)/100 g body weight) than the nondiabetic rats (1.86 +/- 0.25 cm(3)/100 g body weight).

CONCLUSIONS

Compared to nondiabetic rats, diabetic rats suffered a greater blood loss after the same uncontrolled vascular injury.

HEXOSAMINE BIOSYNTHESIS AND PROTEIN O-GLYCOSYLATION

An early and rapid response to severe injury or trauma is the development of hyperglycemia, which has long been thought to be an essential survival response by providing fuel for vital organ systems and facilitating mobilization of interstitial fluid reserves by increasing osmolarity. However, glucose can also be metabolized via the hexosamine biosynthesis pathway (HBP), leading to the synthesis of uridine diphosphate N-acetyl-glucosamine(UDP-GlcNAc). UDP-GlcNAc is a substrate for the addition, via an O-linkage, of a single N-acetylglucosamine to serine or threonine residues of nuclear and cytoplasmic proteins (O-glycosylation, O-GlcNAc). There is increasing appreciation that protein O-glycosylation is a highly dynamic posttranslational modification that plays a key role in signal transduction pathways. Sustained increases in O-GlocNAc have been implicated in the development of diabetes and diabetic complications; however, recent studies have demonstrated that stress leads to a transient increase in O-GlcNAc levels that is associated with increased tolerance to stress. Indeed, activation of pathways leading to O-GlcNAc formation improves cell survival after I/R injury, whereas inhibition of O-GlcNAc formation decreases cell survival. In addition, in rodent models of trauma-hemorrhage, increasing O-GlcNAc levels during resuscitation improves cardiac function and organ perfusion and attenuates the inflammatory response. At the cellular level, increasing O-GlcNAc levels attenuates nuclear factor-kappaB activation. It is noteworthy that other metabolic-based treatments for severe injury such as glucose-insulin-potassium and glutamine also lead to increased HBP flux and O-GlcNAc levels. The goal of this review is to summarize our current understanding of the role of the HBP and O-GlcNAc on the regulation of cell function and survival and to present evidence to support the notion that activation of these pathways represents a novel treatment strategy for severe injury and trauma.

Hyperglycemia in the intensive care unit: no longer just a marker of illness severity

BACKGROUND

Hyperglycemia is a common occurrence in critically ill patients. Recent evidence has demonstrated improved survival in patients in surgical intensive care units (SICUs) receiving "tight glycemic control." The mechanisms of this survival advantage are not well understood.

METHODS

A review of the English language literature pertaining to potential mechanisms affecting outcome in critically ill patients receiving insulin therapy, including recently published human trials evaluating mortality outcomes.

RESULTS

This review discusses the results of clinical trials of "tight glycemic control," considers mechanisms of hyperglycemia in critical illness, and reviews potential mechanisms of improved outcome related in the critically ill patient.

CONCLUSIONS

A number of human studies have demonstrated improved outcomes in critically ill patient populations receiving insulin therapy with a target of euglycemia, suggesting at least part of the benefit of this therapy is normal blood sugar and not the effects of insulin. An important population not studied to date is patients in the medical ICU. However, aggressive control of hyperglycemia now remains an important component of care for all surgical patients in the ICU.

The effect of non-insulin dependent diabetes mellitus on uncontrolled hemorrhage in a rodent model

OBJECTIVE

Diabetes mellitus (DM) is an independent risk factor for higher morbidity and mortality rates from trauma. We tested the null hypothesis that there would be no difference in the hemorrhage volumes and hemodynamic responses to uncontrolled hemorrhage between Zucker Diabetic Fat rats (ZDF) and euglycemic Sprague-Dawley rats (SD).

METHODS

Twenty-four adult male rats (12 ZDF and 12 SD) were anesthetized with althesin via the intraperitoneal route. The femoral artery was cannulated by cut-down to monitor the heart rate (HR), mean arterial pressure (MAP) and to obtain blood samples for blood gas analysis. Twelve rats (6 ZDF and 6 SD) underwent uncontrolled hemorrhage by 50% tail amputation. Twelve rats (6 ZDF and 6 SD) served as non-hemorrhage controls. The HR, MAP, lactate (LAC), glucose levels (GL) and cumulative hemorrhage volume (CHV) were measured pre-hemorrhage and then every 15 min post-hemorrhage for 120 min. Data were reported as mean+/-S.E.M. Group comparisons were analyzed by ANOVA with repeated values; post hoc testing by Bonferroni (all tests were two-tailed, alpha = 0.05).

RESULTS

Pre-hemorrhage the SD and ZDF were evenly matched for LAC, HR and MAP. CHV (cm3/100 g) was significantly (p = 0.008) greater in the ZDF (1.49+/-0.12) as compared to the SD (0.38+/-0.11). The ZDF had significantly (p < 0.001) higher LAC (7.96+/-0.61 mmol/L) than the SD (2.0+/-0.41 mmol/L).

CONCLUSION

DM as compared to non-DM rats suffered a greater blood loss with a more severe lactic acidosis after a comparable uncontrolled vascular injury.

The effects of hypertonic saline in healthy and diseased animals

In this review, the pharmacological effects of administering hypertonic solutions to both healthy animals and during experimentally induced diseases are considered with a view to understanding the mechanisms behind the possible clinical efficacy of such treatment. The review focuses successively on haemorrhagic shock, endotoxic shock and hypokalaemic metabolic alkalosis. How hypertonic saline solutions affect oxygen transport by haemoglobin is also considered.

The serum osmole gap

Estimation and measurement of serum osmolality can be of value in the clinical management of certain forms of critical illness. Osmolality is a measure of the concentration of osmotically active particles, or solutes, in a solution. Only low-formula weight ions and uncharged molecules that are present in relatively high concentrations contribute significantly to serum osmolality. Serum osmolality can be easily estimated from the three major osmotic constituents of normal serum (sodium, urea, and glucose) by a simple formula. An understanding of serum osmolality, its laboratory measurement, its bedside estimation, and the concept of the osmole gap, is crucial in making a preliminary diagnosis of methanol and ethylene glycol intoxication, as well as a few other related compounds. There are important caveats to this use of the osmole gap, because under certain circumstances both false-positive and false-negative interpretations may occur. The osmole gap may also be helpful for confirming pseudohyponatremia, as a gauge for dosing mannitol and glycerol when used to treat intracranial hypertension, and as a prognostic indicator in circulatory shock.

Failure of hypertonic saline to resuscitate intestinal ischemia shock in the rat

The effects of resuscitation with hypertonic saline (HS), administered as a bolus injection or infusion, were studied in a model of intestinal ischemia shock in rats. The model is characterized by severe intestinal mucosal lesions, release of cardioinhibitory substances and endogenous opioid peptides, and it results in high mortality rates. The blood pressure improved after HS given as an infusion for 1 h. The effects on blood pressure of HS given as a bolus and of normotonic saline (NS) were not significant. Plasma volume was not different from unshocked control animals in either HS infusion or NS infusion groups 2 and 4 h after infusion. Liver metabolic consequences of intestinal shock did not differ comparing the HS and NS groups, and the same result was found concerning the mucosal lesions in the small intestine. The 7-day survival decreased in the HS infusion group (14%) compared to untreated shock (46%) or NS infusion (54%) groups. We conclude that HS failed to resuscitate intestinal ischemia shock. These experiments indicate that HS treatment could even, in contrast to previous reports on hemorrhagic shock, be disadvantageous or dangerous in shock states characterized by extensive tissue injury.

Pathophysiology of shock-induced disturbances in tissue homeostasis

A survey is given on disturbances in tissue homeostasis induced by hypovolemic shock conditions. Fluid shifts taking place between the extra- and intravascular fluid compartments are important early compensatory responses following hypovolemia. Usually the supply-to-demand ratio of oxygen in most tissues can however, not be kept up if the hypovolemic insult is severe due to deterioration of the microcirculation. Cellular hypoxia will ensue and may with time affect the integrity of the cells. Cellular functional disturbances occur earlier and are more pronounced in peripheral non-vital tissues such as e.g. skeletal muscle than in central organs, the blood flow of which is more favoured during shock. Anaerobically produced cellular metabolites as well as intracellular components released from hypoxically injured cells in peripheral tissues may be of importance for the initiation of decompensatory reactions. Cellular components reaching the central circulation may induce direct effects on organs or systemic effects due to activation of the cascade systems. Thereby reactions leading to severe complications such as adult respiratory distress syndrome (ARDS), disseminated intravascular coagulation (DIC) and multiple organ failure may be started. The aim of shock treatment should be to reverse as rapidly and as efficiently as possible the pathophysiological disturbances induced by a shock state. If the cellular hypoxic insult can be limited then the incidence of systemic complications in the post-shock period will also be reduced.

Phase-related changes in tissue energy reserves during hemorrhagic shock

In view of the well-known fact that the liver is more sensitive to ischemia than skeletal muscle, it was the purpose of the present study to determine the relationship between the hemorrhage-induced changes in plasma glucose and lactate concentrations and the status of the energy reserves of these two tissues. Sprague-Dawley rats were bled to a constant mean arterial blood pressure of 40 mm Hg and held there by removal or reinfusion of blood. The stages of shock defined on the basis of the net blood loss were early compensatory, maximal compensatory, early decompensatory, and late decompensatory phases. The results showed a depletion of hepatic ATP levels which occurred between the early compensatory and maximal compensatory phases of shock, coincident with the most dramatic increases in plasma glucose and lactate seen during the shock protocol. Hepatic ATP levels fell no further through the decompensatory phases of shock while plasma glucose declined to hypoglycemic levels and plasma lactate was maintained at the same high level attained at the maximal compensatory phase. Since hepatic sources of glucose were exhausted by the maximal compensatory phase and hepatic energy stores were depleted to a point which precludes significant gluconeogenesis, the large increase in plasma lactate was probably largely due to loss of the hepatic "sink" for lactate during this phase of shock. In contrast to the liver, soleus muscle showed no change in the levels of glycogen, ATP, CrP, free creatine, or total creatine compared to time-matched controls in any phase of hemorrhagic shock suggesting the absence of significant muscle ischemia. The possibility that red skeletal muscle may act as a "sink" for lactate is considered.

The response of the awake spontaneously hypertensive rat (SHR) to acute blood loss

In order to evaluate experimentally if the presence of hypertensive disease is an additional risk factor in connection with emergency situations including blood loss, awake spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) were subjected to standardized acute haemorrhage (35% of blood volume) via an aortic catheter. Mean arterial blood pressure (MAP), blood gases, acid-base balance, blood glucose and haematocrit values were followed and the 5-h survival rate was determined. In the early posthaemorrhagic phase similar plasma refill, as evidenced from haematocrit readings, was seen in SHR and WKY. Hyperglycaemia occurred in both groups but the hyperglycaemic response was only moderate and transient in SHR. The inability of SHR to maintain hyperglycaemia was intimately correlated to early appearance of metabolic acidosis and short posthaemorrhagic survival times. Determination of liver glycogen content of unbled SHR and WKY indicated that the deficient hyperglycaemic response in SHR was not due to inadequate glycogen stores but rather to poor liver perfusion resulting in liver hypoxia. Since spontaneous hypertension in rats in many ways is considered to be similar to essential hypertension in man, these findings suggest that human hypertensive disease constitutes a considerable risk factor in connection with acute haemorrhage.

Comparison of isotope dilution technique and haematocrit determination for blood volume estimation in rats subjected to haemorrhage

The method of posthaemorrhagic blood volume (BV) determination by simple haematocrit measurement has been compared with the conventional isotope dilution technique. 51Cr tagged erythrocytes and 125IHSA were used to estimate RBC volume and plasma volume in non-starved male Sprague-Dawley rats. Two series of experiments were carried out by two different investigatory groups. Haemorrhage was inflicted by 60 or 90 min of haemorrhagic hypotension at 70 mm Hg, causing 41% and 56% loss of the initial estimated BVs, respectively. There was agreement in both series for the initial blood volume indices; RBC volume, 2.82 ml x 100 g-1 b.wt.; plasma volume 3.33 ml x 100 g-1 b.wt. and F cells, 0.91. Using the RBC volume data, the calculated residual BVs after haemorrhage corresponded accurately to the isotope measurements in both series. It is concluded that non-splenectomized rats may be used for accurate BV analysis after haemorrhage if the basal data for the strain used are known.

Cardio-vascular and metabolic alterations caused by hemorrhage in fed and starved rats

Non-starved (fed) and starved rats, sedated with a neurolept analgesic, were subjected to 45 min of hemorrhagic hypotension. The hemorrhage inflicted did not cause hypoxic changes, and left fed and starved animals with the same residual blood volume. Fed animals developed a state of hyperglycemic hyperosmolality and their free fatty acids tended to rise, while these observations were modified among starved animals. After 15 min of hemorrhage the cardiovascular parameters were the same in fed and starved animals, but at 45 min striking differences were observed. In fed animals, cardiac output, stroke volume, skin and muscle flows were substantially higher than starved animal values, while the latter animals had a higher heart rate and peripheral resistance. These effects are attributed to the state of hyperosmolality developed by the fed animals, and can explain the association between nutritional status and survival in hemorrhage.

Modification of cardio-vascular responses to hemorrhage by induced hyperosmolality in the rat

Starved rats sedated with a neurolept analgesic were subjected to hemorrhagic hypotension while receiving infusions of iso-osmolar and hyperosmolar solutions. The hemorrhage model used resulted in similar residual blood volumes and hematocrits in all groups. The non-metabolizable pentose, xylose, and glucose were used to induce a state of hyperosmolality, which was absent in those animals which received iso-osmolar infusions (0.29 M xylose). After 45 mins hemorrhagic hypotension and a blood loss equal to 40% of the initial blood volume, the animals receiving the hyperosmolar infusions had a better cardiovascular status compared to those which received the iso-osmolar infusions. The cardiac outputs and stroke volumes were higher and heart rate lower in the hyperosmolar groups. Evidence of better tissue perfusion was obtained in those animals with the induced state of hyperosmolality.